Guide 1: Saving Your Gems For Builders
Should you rush production of buildings or see things through and not pay to rush construction? By waiting, you can save your gems and spend them on more important things in the future. Given the three-day grace period, you have some time to construct your fortifications and defense before people begin attacking. More importantly, you can buy a second builder quicker.
Starting out with a builder, your next builder will cost you 250 gems, and the next one will cost you 500 gems. Where as the 4th and 5th builder, at 1000 gems and 2000 gems respectively, are a bit far away, it is not impossible to have at least the first three relatively quickly. So do not rush your early construction, and instead save your gems for builders!
Guide 2: To Not Invest in Expensive Units
Big, expensive units are fun to play around with and go on the offensive with. That being said, they are not always the most economically viable units. Consider a wizard. A wizard takes 8 minutes to produce. While it is better then an archer, you can create more then 16 archers in the same amount of time. In addition, when considering cost, remember that dragons and giants are both great and costly. Only use them in moderation. Instead, focus on barbarians and other cheap units that are easy to produce and inexpensive. The bonus to focusing on these units is that you can create a defense in relatively little time while keeping a store of supplies to be used for more important means.
By saving your gems for builders and keeping a supply of gems on you for future construction, you can set yourself up for quick expansion in the middle and late game. With enough skill and luck, you will be able to catapult yourself into a commanding position. Until that time, good luck!